: P30 CORE A Well-differentiated primary human airway epithelial cells and the assays that can be used with them are an instrumental model for understanding epithelial biology and are highly predictive of in vivo results in clinical trials. Primary cells can be used with methodologies that translate readily to assays of airway function in vivo, including measures of CFTR activity or other ion transporters, airway surface liquid depth and mucus hydration, and mucus viscosity and transport. Primary airway cells further provide an excellent model for examining the biology of airway epithelial inflammation, which is key to the pathogenesis of cystic fibrosis (CF) lung disease. The purpose of Core A is to support the research of numerous P30 investigators that involves cell culture systems and to assist with established and innovative assays available to characterize cellular responses. Core A carries out three main functions as outlined in the Specific Aims. First, Core A procures, grows, and distributes well-differentiated primary human airway epithelial cells from CF and non-CF donors. This includes samples of cells from lung transplants, surgically excised nasal tissue, and nasal brushings obtained at UAB and from a large array of collaborating centers. Examination of novel expansion and differentiation techniques for primary cells is also a key function of the Core. Second, Core A conducts functional anatomic imaging of airway epithelia by 1-micron resolution Optical Coherence Tomography (?OCT) in vitro (primary cells of human or non-human origin) and ex vivo (intact full-thickness trachea or mainstem bronchi of human origin or comparable tissues from CF animal models, thus interfacing with Core B). ?OCT allows for investigators to explore mucus flow and mucociliary interactions and is designated as a National Core due to its unique and important capabilities. Third, Core A performs and assists with measures of CFTR activity and expression. In addition to traditional assays of CFTR function (e.g, Ussing chambers), the Core supports innovative conductance assays and advanced PCR technology for investigating CFTR and other protein expression. Core A facilitates interdisciplinary collaborative research, provides resources that are beyond the expertise of individual research laboratories, fosters the sharing of ideas and experimental strategies, assists with technical troubleshooting, and maintains essential equipment that is and will be heavily utilized by P30 personnel and beyond. Cost savings are achieved by minimizing duplicate efforts of individual CF investigators, by the centralized purchase and usage of equipment, reagents, and supplies, as well as by maintaining a central repository for human epithelial tissue. On the whole, Core A provides significant expertise and resources to aid P30 investigators, fostering advancement of epithelial cell culture and innovative assays to understand CFTR pathogenesis and support rational drug discovery.